KEPCO BIT 4886 Operator Manual - Manual (Page 57)

BIT 4886 120413
4-23
output off state. DIAG:OUTP n
H
(see Table 4-5) controls the limit DAC values when the output is
set to OFF; n = 0 is the default. This sets both voltage and current limit channels to 0 when the
output is off. n = 1 sets voltage limit to maximum when the output is off. n = 2 sets the current
limit to the maximum when the output is off. Bits 2 and 3 of the hex character allow the
DIAG:OFFLimit commands to establish a specific voltage limit and current limit, respectively,
when the output is off. Bits 0 and 2 or bits 1 and 3 should not be set at the same time since the
maximum setting will override the value specified by DIAG:OFFLimit. The SYST:SEC:IMM com-
mand sets DIAG:OUTP n = 0. The variables are stored in non-volatile EEPROM by the com-
mand MEMORY:UPDATE INTERFACE.
4.7.3 USING AND SAVING SYSTEM VARIABLES
The DIAG:SAV command prepares the variables established by the SYST:SET command see
(PAR. B.90) to be stored and used for subsequent power up cycles. However, executing
SYST:SEC:IMM (PAR. B.89) restores the following configuration for subsequent power up
cycles: LF0, DC0, RO0. In addition to initializing all the variables (except password) to the
default state, SYST:SEC:IMM clears the SAV setup area and performs a PACK of the memory
partitions (see PAR. 4.7.4).
Saving LF1 means that the unit will provide a line feed if the buffer is empty and a read is per-
formed. Saving LF0 means that each string sent to the GPIB port causes a null string to be
transmitted. The null string is a single Line feed character. This command is useful during pro-
gram debug as a read without a query will not hold up the bus.
Saving DC0 means that DCL and SDC have no effect on the device (power supply) except to
clear internal status registers. Saving DC1 means that DCL and SDC commands will function
the same as the *RST command: the output is set to 0 Volts, 0 Amperes, voltage mode is
selected and the output is set to OFF (unless RO1 is also set).
Saving RO0 causes the *RST command to set the output to 0 Volts and 0 Amps and sets output
to OFF, requiring an OUTP ON command to be sent before voltage/current commands are pres-
ent at the output. Saving RO1 causes *RST to set the output to ON and sets the output to 0
Volts and 0 Amps. Subsequent VOLT and CURR commands affect the output directly without
having to send OUTP ON. The OUTP ON and OUTP OFF commands function normally to turn
the output on and off.
4.7.4 FLASH MEMORY EEPROM OPERATION
The unit’s configuration, voltage and current, saved setups (*SAV and *RCL command) and Cal-
ibration values are stored in Flash Memory. Since the Flash EEPROM cannot be modified by
writing a single data byte, the block must be erased and then the data written into the correct
locations.
The BIt 4886 card accomplishes this by partitioning the Flash memory. As the amount of Flash
memory used becomes larger with each subsequent data update, the Flash memory can fill up
and needs to be compressed. The compression of the Flash EEPROM, called packing, is auto-
matically handled by the BIT 4886 microprocessor's code. The packing process can take a half
a second to accomplish. Because it is automatically executed, it can occur after any *SAV,
Memory:UPDATE, or save of Calibration. When the memory is out of space, the internal micro-
processor copies the live data to a backup flash area, erases the main flash data area, copies
the current control variables into this clean space and then erases the backup flash area. The
pack process can take 500 milliseconds to complete. Packing is automatically invoked during
power up initialization if the BIT 4886 card finds that any storage area is over 90% utilized.